Shiva Purana
अन्यथा निरपेक्षेण मूर्तिः स्वीक्रियते कथम् ॥ मूर्तिस्वीकरणं तस्मान्मूर्तौ साध्यफलेप्सया ॥ १२ ॥
Otherwise how is the form adopted by the nondependant? The adoption of form is with a purpose to get the fruit of his desire.
english translation
anyathA nirapekSeNa mUrtiH svIkriyate katham ॥ mUrtisvIkaraNaM tasmAnmUrtau sAdhyaphalepsayA ॥ 12 ॥
hk transliteration by Sanscript